1. Technical Field
The present invention relates to a substrate holding unit, a substrate bonding apparatus, a multi-layered substrate manufacturing apparatus, a substrate bonding method, a multi-layered substrate manufacturing method, and a multi-layered semiconductor apparatus manufacturing method. The contents of the following patent applications are incorporated herein by reference:    No. 2007-281200 filed on Oct. 30, 2007    No. 2008-199553 filed on Aug. 1, 2008    No. 2008-199554 filed on Aug. 1, 2008
2. Related Art
One technique for improving the effective packing density of a semiconductor apparatus involves using a configuration with a plurality of layered dies. A layered semiconductor module in which dies are layered prior to packaging not only has improved packing density of the circuits and elements therein, but also has shorter wiring between the chips to enable faster processing. Furthermore, when manufacturing a layered semiconductor module, there are cases in which the bonding is performed in units of dies, but the throughput can be improved by dicing the layered modules after bonding in units of wafers.
A wafer serving as the material for the layered semiconductor apparatus has a low thickness relative to its surface area, and so does not have a high mechanical strength. Therefore, in order to handle the wafer without damaging it, the wafer is fixed to a fixing member that has a flat adhesion surface, such that the wafer is handled together with the fixing member. When bonding wafers, the bonding process can be easily achieved by bonding the wafers via the fixing members and holding the bonded wafers between the fixing members.
Japanese Patent Application Publication No. 2006-339191 discloses a pair of wafer holders that each include a joining member generating an adhesion force and that are joined to sandwich the wafers bonded therebetween. As a result, the pair of wafers can be held while maintaining the aligned and bonded state.
However, when using permanent magnets to generate the adhesion force, the permanent magnets exert a continuous adhesion force on the magnetic bodies, and so when adjusting the relative positions of the substrates, the magnetic force affects the alignment. Furthermore, when joining the permanent magnets and the magnetic bodies, the substrates experience a large shock at the moment of adhesion if the attractive force exerted on the magnetic bodies is strong, and this may damage the substrates.